The goal of this project is to assess the trace-element status of infants fed human milk versus that of infants fed prepared formulae. This goal is broken down into the following objectives: 1. To determine the trace-element content of human milk, cow's milk, and prepared infant formula using instrumental and radiochemical neutron activation analysis (NAA). 2. To assess the effect of maternal diet on trace element concentrations in human milk over the nursing period. 3. To assess the infant's trace-element status by analyzing serum samples obtained at weaning or a similar time for formula fed infants. NAA is a sensitive analytical method for many trace elements such as Se, Hg, I, V, Cs, Cr, Ni, Sc, Rb, Fe, Zn, Co, Sb, Eu, or Mn. Objective #1 is to be accomplished during the first year on samples of cow's milk and formulae obtained commercially and on samples on human milk obtained from volunteers over a one week period. Objective #2 is scheduled for the following year where volunteer new mothers will keep a dietary record (including medication and supplements) and provide milk samples at set intervals over the nursing period. Objective #3 is to begin after Objective #2 ends with 5 ml blood samples to be obtained from the infants of the mothers participating in the Objective #2 study.